Conventional pressure calibration systems are normally large, heavy stationary systems, incapable of convenient transport. In addition, when compressed gas pressure sources are connected to equipment to be calibrated, fine adjustment of the regulated calibration pressure has proved difficult.
Volumetric "vernier" adjustment controls changing the volume in the test conduit system by small amounts have been proposed, to provide such fine adjustments of calibration pressures, but separate isolation valves first connecting the source of pressure or the external vent to the test conduit system, and then isolating the test conduit system, have proved difficult to operate, requiring careful control and time-consuming manipulation of different valves in order to complete the calibration operation.
Accordingly, a significant need has developed in military, industrial and commercial applications for lightweight, portable pressure calibrating systems and devices which can be readily connected to pressure transducers and gages to be calibrated. Quick and convenient manual control of such systems for connecting and adjusting the regulated supply pressure have been recognized as a significant objective to be achieved, but successful devices and systems meeting this objective have not been manufactured or marketed, before the present invention.
Accordingly, a principal object of the present invention is to provide reliable high-pressure calibration systems and devices capable of accurate pressure calibration over a working range extending from a vacuum to 10,000 psi.
Another object of the invention is to provide such systems and devices which are light in weight, and conveniently portable.
Still another object of the invention is to provide such systems and devices which are capable of accurate and precise "vernier" adjustment of calibrating pressures over the entire working range.
A further object of the invention is to provide such systems and devices incorporating automatically actuated isolation valves capable of isolating the vernier pressure control system from supply pressure and from the atmosphere during the calibration process.
Still another object of the invention is to provide such pressure calibrating systems and devices whose manual valve controls are actuated by extremely low torque permitting fingertip adjustment.
A still further object of the invention is to provide such systems and devices capable of producing a firm, positive shutoff, disconnecting the pressure source and the atmosphere from the systems being calibrated, while requiring extremely low torque for actuation.
An additional object of the invention is to provide such pressure calibrating systems and devices incorporating soft valve seats, cooperating with fine valve needles to minimize the frictional engaging force produced by closing each valve to its shutoff position, with convenient adjustment of the closed valve position to compensate readily for valve seat wear.
Still another object of the invention is to provide such pressure calibrating devices incorporating pressure, vent and vernier valve mechanisms all of whose moving parts can be removed and replaced through the front panel of the device, avoiding disassembly for servicing.
Other objects of the invention will in part be obvious and will in part appear hereinafter.
The invention accordingly comprises the features of construction, combinations of elements, and arrangements of parts which will be exemplified in the constructions hereinafter set forth, and scope of the invention will be indicated in the claims.